Dinosaur may be second-biggest yet found

For Joshua Smith, it seemed like a good deal: He'd help his archaeologist fiancee at a dig in Egypt, and she would help him scrape around for a day or so at an oasis virtually untouched by paleontologists since 1935.

But the modest bargain has yielded some gargantuan results.

Mr. Smith's plan for a desert day trip triggered a seven-week expedition that has uncovered one of the largest dinosaurs ever to walk the planet.

Reaching 80 to 100 feet from snout to tail, and tipping the scales at up to 70 tons, the creature appears to be a close relative of the largest vertebrate yet found, 90-ton Argentinosaurus, discovered in Argentina in 1988.

The new creature, which Mr. Smith and his colleagues named Paralititan stromeri, was found among a wealth of plant and animal fossils from the same period, 94 million years ago. Researchers say the find will help fill a vexing gap in the fossil record during the Late Cretaceous period as well as from that part of the world.

The find, they say, also could shed light on the emergence of today's continents from one supercontinent. And the wealth of plant and animal remains could hold important clues to how Earth's biosphere responds to climate change.

"We may have stumbled onto dinosaur heaven at Bahariya," says Smith, a Ph.D. candidate in the earth and environmental sciences department at the University of Pennsylvania in Philadelphia and the leader of the team reporting its results in today's edition of the journal Science.

To look at the Bahariya Oasis today, heaven might be the last word that springs to thought. Located 180 miles southwest of Cairo, the oasis appears as a patch of palm-frond green set amid the tawny hues of desert shale and sandstone.

Everglades-like dinosaur haven

Ninety-four million years ago, however, the area was a tropical tidal flat blanketed with mangroves, much like today's coastal Everglades, the researchers say. And the area was highly productive biologically. In addition to Paralititan, the team found fossils of crocodile-like creatures, crabs, coelacanth and other fish, other large sauropods like Paralititan, and three carnivores about the size of Tyrannosaurus rex.

To the creatures that thrived there, the area was the biological equivalent of a Late Cretaceous supermarket. "The amount of biomass in the area had to be enormous to support all that," Smith says.

Ultimately, Paralititan (which means "tidal giant") appeared to be on something's grocery list. The team found evidence that their find had been gnawed by a meat eater.

How the great beast came to fall will likely remain a mystery. The evidence suggests that it became a meal after it fell, says Thomas Holtz Jr., a paleontologist at the University of Maryland at College Park. Even big creatures with razor-sharp teeth would have balked at attacking so large an animal, unless they hunted in packs.

While no evidence has emerged that such hunting behavior existed in the area, Dr. Holtz notes that other researchers working at a site in Argentina have found T-rex-size carnivores of about Paralititan's age that appear to have lived, and perhaps hunted, in groups.

Paralititan's discovery marks a paleontological renaissance for the Bahariya Oasis. From 1915 to 1935, Bavarian geologist Ernst Stromer pulled a large number of fossils from the oasis and shipped them to Munich. But in 1944, the museum there was pulverized by Allied bombers.

The only surviving records of Stromer's discoveries are "a few old monographs with beautiful plates" illustrating the fossils, says Hans-Dieter Sues, a vertebrate paleontologist at the University of Toronto.

Dr. Sues, who describes Smith's find as "fantastic," says that, while the discovery yields creatures similar to those identified at other North African sites, the Bahariya fossils are more complete, compared with the isolated bones and teeth found elsewhere.

He also notes that the research team's find is important for the time gap it helps fill.

The latter half of the Late Cretaceous period, which marked the dinosaurs' final millennia on the planet, is the best-documented, Sues says. The early part of the Late Cretaceous, when Paralititan thumped across the landscape, "is a big blank" from the standpoint of fossils. Yet it also is a period that appears to represent a final evolutionary shift in dinosaurs that scientists would like to better understand, he says.

Climatic and continental puzzles

Bahariya's fossils also could open a window for paleoclimatologists trying to reconstruct Earth's climatic history, Holtz notes.

"This was one of the hottest intervals in Earth's history, with the smallest temperature difference between the equator and the poles, the highest ratio of ocean to land cover, and very high carbon-dioxide levels in the atmosphere," he says, adding that the fossil record suggests that amid these conditions, the Earth was highly productive biologically. The period may shed some light on how the ocean, atmosphere, and biological activity interact at a time of high carbon dioxide concentrations.

The Penn team's find also may help pinpoint the deconstruction of Gondwana, a supercontinent from which South America, Africa, Antarctica, Australia, India, and Madagascar split during the dinosaur age.

One notion, Holtz says, holds that Africa lost its physical connection to the other pieces well before the Late Cretaceous, while the remaining segments kept their links.

"New data support the idea of a faunal connection between Africa and South America into the beginning of the Late Cretaceous because animals are so similar between the two land masses," he says. "This adds yet another, very similar form."